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Characterization of bulk materials
Focus on flow behavior, cohesion & manageability
causes of differences
The reason for differences in the handling of a bulk material is often the different flow properties. We measure the flow properties of your bulk material.
Strongly cohesive bulk solids have transport, conveying, dosing and storage properties that are difficult to handle. These macroscopic bulk solid properties depend on moisture, particle shape, surface properties, particle size distribution and cohesiveness.
The aim is to work with extended characterization properties that differentiate between the use cases.
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Ring shear measurements
The flow function coefficient (FFC) of a bulk material describes the relationship between the maximum principal stress determined in the Mohr circle and the compressive strength, and is a key measure of powder handling. A higher FFC value indicates better flowability. This measurement is referred to as determining the yield locus (FO).
The stresses required for the calculation are derived from Mohr stress circles, which are determined using a ring shear analysis according to Dietmar Schulze. This method enables a realistic assessment of the flow behavior under practical loading conditions.
The time consolidation of a bulk material – also known as caking behavior – is also determined using the ring shear tester and allows a statement to be made about how strongly a bulk material solidifies during storage (a prerequisite for this measurement is a previous determination of the yield locus FO of the same bulk material).
For this purpose, the sample is stored in a time consolidation bench under the normal stress determined at the yield locus (FO) for a defined period of time—e.g., 6 hours. This ensures that the bulk material is exposed to the same mechanical stress throughout the storage period as during the yield locus measurement.
After storage, a shear test is performed, during which the changed flowability (FFC) is measured. This measurement is referred to as the determination of the yield locus (FO) and indicates whether and to what extent the material has solidified during storage.
This method allows the flow behavior and storage stability of a bulk material to be quantitatively evaluated and related to each other – an important basis for the processing-related assessment.
If you are interested in measurements with the ring shear tester, please feel free to contact us.
Ring shear tester according to Dietmar Schulze
ASTM D-7891 - 15 Standard Test Method
We look forward to your inquiry!